This invention relates to a roller assembly which passes through predetermined points in its travel for use in the field of cargo mover systems, such as in elevators, escalators, and moving walkway systems. More particularly, this invention relates to a rim assembly for the roller assembly of such a system. This invention was developed for lightweight roller assemblies used with elevator doors as the doors are moved between the open and closed positions and has application to other roller assemblies following a defined path used for cargo mover systems.
Roller assemblies used in escalator systems and elevator systems typically pass through predetermined points that form a defined path. These systems are of the type that are typically self-propelled or driven externally. The systems that are driven externally may be driven by a cable, belt or chain of both the open or endless type, or by a mechanical mechanism utilizing screw drives or lever arm actuation. In these systems, the roller assembly and the rail on which the roller assembly moves are a defined portion of the system. For example, the shape and the surface characteristics of the rail surface are defined. Since the rail surface is well-defined, expectations for life, low noise and other characteristics are greater than expectations for roller assemblies used on undefined surfaces, such as might be experienced by bicycles, automobiles and moving carts.
Roller assemblies used in escalators and elevators typically have a rim assembly which includes a rim and a ring in solid form that is positioned from the rim. The ring in solid form has requirements for operative characteristics that are very different from the operative requirements for a ring which is in part supported by gas under pressure, such as automobile tires and the like. In particular, roller assemblies used for elevator doors especially have significant requirements for operative characteristics that can be in conflict. Such roller assemblies may be driven or nondriven.
In contrast, roller assemblies used for guiding elevators or used for escalator systems do not have as many demanding operative characteristics even though the roller assembly follows a defined path. Escalator systems typically use nondriven roller assemblies. For example, the nondriven roller assembly may be attached to an operating element for guiding the element, such as a step chain in the escalator system. One example is shown in U.S. Pat. No. 5,137,135 entitled xe2x80x9cEscalator Step-Chain Rollerxe2x80x9d issued to Pietsch et alia. The roller assembly includes a rim assembly having a rim. The rim has a groove bounded by a surface which faces outwardly. A flexible outer ring in solid form is disposed in the groove and is spaced axially from the sides of the groove. The ring has a rolling surface for rolling contact with a second element. In Pietsch, the cooperating second element is an escalator track.
Elevator systems employ both nondriven roller assemblies and driven roller assemblies that have a ring in solid form. Nondriven roller assemblies may be used for guiding movement of an elevator car as the car moves vertically between predetermined locations. These guide roller assemblies are similar to the roller assembly shown in Pietsch and have somewhat similar operating requirements. The guide roller assemblies are distinguished by the need for the roller assembly to rotate at relatively high speeds in comparison to the escalator roller assembly to accommodate the speed of the elevator car.
As discussed earlier, elevator systems also employ door roller assemblies for guiding elevator doors on the car as the doors are opened and closed. The roller assemblies rotate at a lower rotational speed than do guide rollers for guiding the elevator car. The door roller assemblies are lightweight and may be non-driven, rolling as the door is moved; or may be driven, rotating to drive the door.
A nondriven roller assembly may be attached to the door and may roll on a track as the door is moved by another device between the open and dosed positions. A driven roller assembly engages the track and might be attached to the door. These driven roller assemblies, or traction roller assemblies, are driven about an axis of rotation to move the door between the open and closed positions. An example of such a motorized roller assembly is shown in U.S. Pat. No. 5,852,897 entitled xe2x80x9cDoor Drivexe2x80x9d issued to Sukale.
FIG. 1 is a simplified side elevation view of a roller assembly, such as a lightweight roller assembly 10 for elevator doors, and of a rail 12 on which the roller assembly moves. The rail has a plurality of predetermined location points P which form a defined path 13 for the roller assembly
The roller assembly has an axis of rotation A. FIG. 2 is a cross-sectional view taken through the simplified roller assembly and the rail along the lines 2xe2x80x942 of FIG. 1. The cross-sectioning plane contains the axis A and passes through the circumferential location L. The circumferential location L is the location at which the maximum force is transmitted from the rail to the roller assembly as the rail reacts to the load imposed by the roller assembly on the rail.
As shown in FIG. 1 and in FIG. 2, the roller assembly 10 has a rim assembly 14. The rim assembly is usable with both a driven and a nondriven roller assembly. The rim assembly has a freestanding rim 16 and a groove 18 bounded by a radially outwardly facing surface 20. A flexible ring 22 in solid form is disposed in the groove. The ring extends circumferentially and axially about the rim.
The ring 22 has an outwardly facing surface 24. The outwardly facing surface includes the rolling first surface 26 which adapts the roller assembly to engage the rail. The rolling first surface has an axial width Rs. The rolling first surface under a particular operative condition of the roller assembly is limited to that portion of the outwardly facing surface, which contacts the rail.
A first element, as represented for example by a shaft 28, is attached to one of the doors. The shaft is disposed about an axis of rotation A. In alternate embodiments the shaft might be part of the roller assembly and attached to another portion of the first element. The rail 12 is a second element and is engaged by the roller assembly 10. The roller assembly includes a bearing, as represented for example by a sleeve bearing 32 or a roller bearing as shown in Pietsch. The bearing is disposed between the shaft and the rim assembly to enable movement of the rolling first surface 26 of the ring on the rail.
The rim 16 positions and supports the rolling surface of the flexible ring 22 under operative conditions through a support region R against loads acting on the rolling surface. The ring 22 forms the support region R for the rolling surface in the operative condition. The support region extends radially from the rolling surface to the rim and across the width Rs of the rolling surface. In the embodiment shown, the lightweight roller assembly is not absolutely constrained against movement except for the engagement between the ring and the rail. In one sense, it is a self-guiding roller assembly.
The above art notwithstanding, scientists and engineers are working under the direction of applicants assignee to develop new materials or to develop alternative designs and methods for forming a rim assembly having a flexible ring in solid form which would enhance one or more operative characteristics of the rim assembly under different operative conditions.
This invention is in part predicated on the realization that cargo mover systems use different kinds of roller assemblies for following a defined path with a flexible ring in solid form. The roller assemblies have operative characteristics which may markedly differ depending on the application chosen for the roller assembly or, in a particular application, may change as operative conditions of the cargo mover system change.
A flexible ring is considered to be in solid form where the material of the flexible ring does not rapidly assume the shape of a container in which it is disposed as does a gas or a low viscosity liquid; and, where the average radial height A of the ring is at least sixty (60) percent of the radial distance from the rolling surface of the ring to the support rim. The term xe2x80x9cringxe2x80x9d means annular constructions of flexible material of one or more annular parts that have surfaces in faying contact over at least a portion of the circumference of the ring. The ring provides a radial load path from the rolling surface to the rim and may have continuous circumferential elements or one or more circumferential elements having relatively small circumferential gaps which present the appearance of a ring shape, such as might be used if there is a need for xe2x80x9cnoisexe2x80x9d under operative conditions.
Typically, the flexible ring is circumferentially continuous. One example of such a roller assembly is a lightweight roller assembly used with elevator doors. The roller assembly may require a ring having acceptable load bearing and rolling characteristics that are supplemented with a need for a noise-damping characteristic (vibrational energy damping characteristic). In a driven roller assembly system, the friction or traction characteristic is more important because slipping between the ring and the rail directly effects operation of the doors.
Many flexible materials provide a mix of these operative characteristics. This frequently requires using flexible materials having many operative characteristics that are desirable when used with elevator door systems but also requires accepting some operative characteristics that are less than ideal.
For example, a material providing an acceptable service life and rolling characteristic might have a less than ideal friction characteristic and damping characteristic. This may cause elevator passengers to notice slow door speed or elevator door noise by having these annoyances intrude into their consciousness. On the other hand, providing an adequate damping characteristic might require using a material having a poor rolling characteristic, causing a flat spot to form on the rolling surface which results in noisy operation. Still another compromise might result in using a material having better friction characteristics but which is less durable. Then, noise might result from wear on the surface of the ring. The significance of these concerns increases for door roller assemblies because of the close proximity of the roller assembly to passengers as the doors open and close.
This invention is also in part predicated on the recognition that improved operative characteristics may result from using a roller assembly having special features for any of the preceding applications, and particularly for a door roller assembly. The special features include having a ring in solid form backed with a radial cavity, having a ring in solid form that has more than one part or more than one material, or having a ring in solid form which provides a combination of these features. This permits selecting a material for the surface based on operative characteristics related to surface behavior. These include, for example, cut characteristics, tear characteristics, wear resistance characteristics, resistance to fluid exposure characteristics and friction or traction characteristics. The special features permit modifying operative characteristics of the rim assembly relating to bulk behavior from the bulk behavior characteristics expected from use of the material selected for the rolling surface. Characteristics relating to bulk behavior include rolling resistance characteristics, deformation under load characteristics, damping characteristics and hysterisis heating characteristics. As a result, the bulk behavior of the rim assembly could differ from that which might normally be expected when using the material of the surface as taught by prior art constructions.
According to the present invention, a method for forming a rim assembly for a roller assembly includes disposing a ring in solid form about the rim, forming the rolling surface with a first layer of first material selected for an operative characteristic related to surface behavior; and, providing structure inwardly of at least a portion of the rolling surface which changes an operative characteristic relating to bulk behavior from the operative characteristic that an identical rim assembly would have when entirely filled with the first material in the radial direction.
According to the present invention, the flexible ring is in solid form, has at least a first layer of material which forms the rolling surface to effect the interaction of the flexible ring with the environment; and has a support region for the rolling surface which is defined by the location of the ring radially inward of the rolling surface under operative conditions; and, in the uninstalled condition, the layer of first material is located such that the layer does not entirely fill the space of the support region that exists over the axial width of the rolling surface under operative conditions either because the outer layer of first material deforms under operative loads into a cavity which exists radially below the outer layer in the uninstalled condition or because the support region includes both the material of the first layer and another, different material.
In accordance with one detailed embodiment of the present invention, a rim assembly for a door roller assembly has a first material selected for the rolling surface of the rim assembly and has a stiffness characteristic which is less than about ninety (90) percent of the stiffness characteristic of a rim assembly having a ring having the same contour for the rolling surface with the ring and any portion of a cavity radially between the ring and the rim filled entirely with the first material.
In accordance with one detailed embodiment of the present invention, the ring is formed of a first layer of material having the rolling surface and at least one layer of a different material disposed radially inwardly of the first layer of material.
In accordance with another detailed embodiment of the present invention, the first layer of material has discrete cavities disposed within the layer and filled with a different flexible material.
A primary feature of the present invention is a roller assembly having a rim assembly. The rim assembly has a rim and a flexible ring in solid form. The flexible ring has a rolling surface. A primary feature of one embodiment of the present invention is a rim assembly having an operative characteristic relating to rolling behavior at the rolling surface established in part by the material of the rolling surface and a bulk behavior characteristic for the rim assembly which differs from the expected bulk behavior characteristic of a rim assembly having no cavities and having a flexible ring in solid form which is formed entirely of the material used for the rolling surface. In one detailed embodiment, the rolling surface is concave. In one embodiment, the flexible ring has a first layer of a first material. A feature is a groove which adapts the rim assembly to receive the ring. In one detailed embodiment, the first material is disposed in the groove and spaced radially from the rim. In another detailed embodiment, a second layer of material is disposed radially inwardly of the first layer of material.
A principal advantage of the present invention is the performance of a roller assembly which results from establishing the rolling characteristic of the rim assembly (and thus the roller assembly) with a first material and modifying the bulk behavior characteristic of a roller assembly from that which is expected from using the first material throughout the rim assembly. Another advantage is the rolling characteristic which results from being able to tailor the response of the rolling surface to exterior loads by varying in the axial direction the radial stiffness of the flexible ring which forms the rolling surface. Still another advantage of the present invention is the design and manufacturing flexibility for forming a roller assembly which results from combining, for example, a single material or at least two different materials and a cavity for forming the rim assembly. Another advantage is the ability to tailor the response of the rim assembly to different applications or to retrofit changes to an existing application without changing the external contour of the rim assembly. In one embodiment, a principal advantage is the noise for a given amount of traction which results from using a relatively soft material for the inner layer as compared to the outer rolling layer or which results from disposing a cavity beneath an outer layer to decrease the effective stiffness of the structure.
The foregoing and other features and advantages of the present invention will become more apparent in light of the following detailed description of preferred embodiments thereof as discussed and as illustrated in the accompanying drawings.